Stroke patients with locomotor impairment and gait abnormalities require interventions to enhance the beneficial effects of physical training. The cerebellum is important for making walking smooth, accurate, and adaptable. We have shown that individuals with cerebral damage retain their ability to use some cerebellum dependent learning mechanisms to temporarily improve walking, suggesting that these mechanisms could be useful in rehabilitating gait impairment. Specifically, training stroke patients with gait asymmetries on a split belt treadmill resulted in after-effects that induce a more symmetric locomotor pattern. This effect is promising, since it shows that these individuals still have the neural flexibility to change their gait pattern. However, this beneficial effect is short-lived with return to baseline abnormalities. Transcranial direct current stimulation (tDCS), a form of non-invasive non-painful stimulation, can modulate corticomotor excitability and enhance motor performance and learning of hand motor tasks when applied over the sensorimotor cortex. However, whether tDCS can enhance locomotor function when applied over the cerebellum in healthy and stroke patients is unknown. Here, we proposed to test the hypothesis that cerebellar tDCS will enhance locomotor adaptation in healthy and stroke patients with cerebral damage. In a parallel double blind design, aim 1 will determine in healthy individuals the effects of cerebellar tDCS (anodal, cathodal or sham) on (a) locomotor adaptation using motion analysis, and (b) corticospinal excitability changes using transcranial magnetic stimulation (TMS). Aim 2, will use a similar design, to study behavioral changes resulting from cerebellar tDCS in stroke patients with gait abnormalities due to cerebral damage. This investigation will use two powerful and complimentary technologies to clarify the potential use and underlying mechanisms of a new scientifically sound strategy to enhance locomotor function after stroke. There is no universally accepted treatment to enhance training effects after stroke. In this setting, cerebellar tDCS could evolve into an economical and easily implemented strategy to help address a significan public health burden, gait impairment after stroke. PUBLIC HEALTH RELEVANCE: This proposal will investigate the behavioral and physiological effects of applying transcranial direct current stimulation (tDCS), a form of non-invasive non-painful stimulation, to the cerebellum. The goal is to enhance cerebellar function, which would result in an improvement in locomotor learning. We will test this intervention in healthy individuals and stroke patients with gait impairment. If successful, tDCS could become an easy and inexpensive therapeutic intervention to enhance locomotor training in stroke patients and other neurological conditions.